1. Field of the Invention
This invention relates to a novel nucleic acid sequence coding for the Gβ3-subunit of the human G protein and the use of the Gβ3 subunits of the G proteins for determining the risk of contracting a disease which is associated with a G protein dysregulation.
2. Description of Related Art
Heterotrimeric guanine nucleotide-binding proteins (G proteins) are of outstanding importance in intracellular signal transduction. They mediate the relay of extracellular signals after stimulation of hormone receptors and other receptors which undergo a conformation change after receptor activation. This leads to activation of G proteins which subsequently can activate or inhibit intracellular effectors (for example, ion channels, enzymes). G proteins control intracellular signal processing after hormone stimulation of heptahelical receptors in the cell membrane, but also after stimulation of receptors with intrinsic tyrosine kinase activity. Regulated cell functions include among others cell division and cell growth, contraction, release of cell contents, and much more.
Heterotrimeric G proteins are composed of three subunits, the alpha, beta and gamma subunits. To date several different alpha subunits, 5 beta subunits and roughly 12 gamma subunits have been detected using biochemical and molecular biological methods (Bimbaumer, L. and Bimbaumer, M., Signal transduction by G proteins: 1994 edition. J. Recept. Res. 15: 213-252, 1995; Offermans, S. and Schultz, G. Complex information processing by the transmembrane signalling system involving G proteins. Naunym Schmiedebergs Arch. Pharmacol. 350: 329-338, 1994; Nuernberg, B., Gudermann, T. and Schultz, G. Receptors and G proteins as primary components of transmembrane signal transduction. Part 2, G proteins: structure and function. J. Mol. Med. 73:123-132, 1995; Neer, E. J. Heterotrimeric G protein: Organizers of Transmembrane Signals. Cell 80: 249-257, 1995; Rens-Domiano, S. and Hamm, H. E. Structural and functional relationships of heterotrimeric G proteins. FASEB J. 9: 1059-1066, 1995).
The receptor-mediated activation of certain alpha subunits can be inhibited by pretreatment with pertussis toxin (PTX). They include especially the alpha isoforms alpha-11, alpha-12 and alpha-13 and different alphao-subunits. These G proteins are also called “PTX-sensitive G proteins”.
Betagamma subunits perform important functions in G protein activation and in the modulation of intracellular reactions. All previously known G protein beta subunits on the level of the nucleotide sequence and on the level of the amino acid sequence have high homologies. In this respect these similarities are found not only within the human beta subunits (Gβ1, Gβ2, Gβ3), but also in comparison with beta subunits of other species, for example fruit flies or yeasts.
Recently a base change in exon 10 (C825T) which leads to alternative splicing of exon 9 was described in the human GNB3 gene which codes for the Gβ3 subunit. Alternative splicing is promoted by a cryptic splice site in exon 9, the base exchange C825T which is located farther away intensifying the splicing. The alternative splice product (Gβ3s) has a loss of 123 bp (=41 amino acids). The GNB3-825T allele is associated with increased activation capacity of G proteins and essential hypertension (Siffert, W., Rosskopf, D., Siffert, G., Busch, S., Moritz, A., Erbel, R., Sharma, A. M., Ritz, E.; Wichmann, H. E., Jakobs, K. H., and Horsthemke, B. Association of a human G protein β3 subunit variant with hypertension. Nat. Genet. 18(1): 45-48, 1998; Clapham, D. E. and Neer, E. J. G protein betagamma subunits. Annu.Rev.Pharmacol.Toxicol. 37:167-203, 1997; Hamm, H. E. and Gilchrist. A. Heterotrimeric G proteins. Curr. Opin.Cell Biol. 8:189-196, 1996).
This human GNB3 gene has been described by Levine et al. (Levine, M. A., Smallwood, P. M., Moen, P. T. Jr., Helman, L. J. and Ahn, T. G. Molecular cloning of β3 subunit, a third form of the G protein beta-subunit polypeptide. Proc.Natl.Acad.Sci. U.S.A. 87(6), 2329-2333 (1990)).